Field of the Invention
The present invention relates to liquid crystal display (LCD) technology, and more particularly to an organic thin film transistor (OTFT) array substrate and a fabrication method thereof.
Description of Prior Art
An OTFT is a thin film transistor composed of an organic compound which acts as a semiconductor material, and the OTFT can be produced at low temperatures or at room temperature. Accordingly, lighter, thinner, and cheaper plastics can be chosen as a substitute for glass to be used for an OTFT substrate. The fabrication process for the OTFT is simple in comparison with that of a conventional inorganic thin film transistor because its requirements in environmental conditions for film forming and in purity are lower, so that its fabrication cost is less. Its features such as simple fabrication processes and an excellent flexibility enhance its opportunities of applications in many areas, e.g. fields of flexible displays, electronic skins, flexible sensors, and so forth.
In conventional OTFT fabrication solutions, generally multiple masks, lithography, and etching processes are required to complete a fabrication of an OTFT array substrate. If the number of processes in masks, lithography, and etching required in an OTFT array substrate can be decreased, then the process time of the OTFT array substrate can be shorten and its cost of fabrication processes can be reduced. In addition, a metal material having a lower working function such as silver (Ag) is generally chosen as the electrode material of the OTFT at the present time in order to reduce contact resistance. However, Ag without being covered with a protective layer is easily oxidized and results in a deteriorated conductivity.
In response to these problems, the present invention provides a new method of fabricating an OTFT array substrate, not only the overall number of processes in masks, lithography, and etching required in the fabrication of an OTFT array substrate can be decreased, but also electrodes in the metal layer, e.g. Ag electrodes, can be protected to prevent oxidation of the electrodes from occurring in the subsequent processes. Furthermore, an impact on the quality of a device made of the OTFT array can be avoided.